The use of corks stoppers for retention and sealing of liquids in containers is well known since ancient times. In particular, cork stoppers are preferably used in wine bottles or other alcoholic beverages.
The wide use of corks stoppers to close and seal wine containers and other alcoholic beverages is due mainly to the specific characteristics of cork, such as its elasticity and compressibility. The cellular structure of cork provides the sealing of containers having wine, in order to allow the wine to nurture harmoniously inside the container. This is of outmost importance as it is directly related with the organoleptic characteristics of the wine.
The insulation from the outside environment of the bottle is one of the crucial factors for the appropriate development of a wine, particularly still wine, as it is necessary to prevent contaminations and owners infiltrations, which in excessive levels modifies the wine composition. Therefore, oxygen is frequently responsible for wine deterioration. Obviously, it is also essential to prevent leakage of wine when the bottle is horizontally stored. Thus, seating of stoppers is a crucial element in the selection of appropriate stoppers
One of the major problems that cork stopper producers face these clays is the lack of means for precise measurement of the sealing ability of cork stoppers, allowing carrying out an individual selection, totally reliable, of the cork stoppers that provide a sealing ability in accordance with an objective criterion.
It is known that the problems associated with poor sealing of a container are caused by defects on the surface and inside the body of the cork stopper.
In the contest of the present invention, it should be pointed out the defect named “wormhole” (“bicho”) in the art. This defect is recognized by the person skilled in the art due to the presence of holes and/or channels made by ants or other insects during the natural development phase of cork on the cork oak.
The sealing ability of a stopper is compromised when said channels extend between both end faces (also designated extremities) of the stopper or between the areas of the stopper body near and contiguous to these faces. In these cases, a liquid and/or gas communication is established between the end part of the stopper that is inside the bottle neck and the opposing end part of the same stopper that is facing the outside of the bottle neck. This fluid communication is responsible for early deterioration or even leakage of the liquid stored in the bottle.
More specifically, there is in the art a lack of technical means for checking out precisely if there are communicating channels between the plurality of non-communicating holes and/or channels usually present in a cork stopper, wherein, in many cases, these holes/channels are not even noticeable for the human operator.
To circumvent this problem, the persons skilled in the art have used accessory techniques that aim to increase the reliability level of the sealing ability of the stoppers. Examples of the above mentioned are the arrangement of cork disks at the stopper end which lays inside the bottle; colmatation of cork stopper; and arranging aluminium covers on the outside of the bottle neck. However, these techniques do not assure the intended result and in addition increase the general costs of the stopper production process.
Therefore, the current attempts to solve insufficient sealing of the cork stoppers, yield direct and indirect costs and impart significant resource consuming.
Several processes which can be used at the industrial level have been developed over the years in order to select cork stoppers having a better ability for sealing containers, namely bottles of still and sparkling wine.
Traditionally, the selection of cork stoppers is carried out through visual inspection by specialized technicians. These technicians look for defects, such as those mentioned above and others, on the surface of the inspected cork body that can be interpreted as potential compromisers of the sealing ability. This analysis can also take place directly in cork boards from which corks stoppers are obtained. In this way, after visual inspection, the cork stoppers are classified in different quality classes and the cork boards are approved for production of cork stoppers or discarded for other applications.
Understandably, the visual process by human operators for the assessment of the structural integrity of cork stoppers, in order to predict its sealing behaviour, is an empirical not reliable process, although the substantial experience held by the specialized technicians.
In order to make the process of visual inspection of the outside surface of cork stoppers more efficient and faster, several automatic processes and systems have been developed over the years. One of these processes is described in patent application PT 103749. In this application an automatic method and system of quality control of corks stoppers comprising means for capturing images using visible radiation of the outside surfaces of cork stoppers is disclosed. The obtained images are compared with predefined parameters in order to classify the stoppers according with the presence of defects.
These processes comprising surface inspection of the cork stoppers, even very extensive, have considerable unreliability associated therein, as they do not take into account the internal structure of the cork stoppers.
In order to complement the visual inspection of cork stoppers, processes to analyse their internal structure had been developed. One of these processes is described in the recent patent application PT 104902, which discloses a “Non-destructive and non-invasive method for inspection of plant materials based on the use of electromagnetic radiation”. This method comprises a non-invasive and non-destructive monitoring (using electromagnetic radiation) of internal parameters of natural cork stoppers (such as areas of a stopper with different densities) and subsequent storage of data collected in this monitoring process in a database. The collected data are then used to create a correlation between cork defects and permeability to gases, namely, oxygen. In other words, it is a prediction method of the sealing ability of cork stoppers and, as such, it requires time to create a well defined correlation. Nevertheless it only provides a prediction of the sealing ability.
This type of processes allows correlating the permeability to oxygen with the presence of defects inside of a cork stopper, taking also into account the internal structure of the stopper. However, they are confined to an estimation of the sealing ability of a cork stopper, not providing precise data for each individual cork stopper.
Therefore, both the merely superficial (visual) analyses and the analyses that take into account the internal structure of cork stoppers do not produce precise results when each cork stopper is taken individually. In fact, tests carried out by the process of the present invention have noticed a deficient sealing in cork stoppers considered suitable by the mentioned processes and vice versa, as it is hereinafter demonstrated in the present description.
On the other hand, the practical experience of wine producers and consumers and cork stopper producers has shown the existence of countless cases of deterioration of bottled wine, or even leakage of wine, when such incidents would not be expected nor desirable. These situations unequivocally show that, despite the efforts made by the cork industry, sealing deficiencies still persist that require resolution.
Accordingly, there is a need for an efficient process and device that can be industrially applied, that provide a real and objective measurement of the sealing ability of each tested cork stopper, in order to eliminate the deficiencies of statistics and visual analysis ascribable to the processes and systems of the prior art and, therefore, to contribute for a truly significant effectiveness in the selection of cork stoppers.